Merge pull request #11079 from grpc/revert-10982-master

Revert "Documentation on how to write unit tests using auto-generated mocked stubs."

doc/unit_testing.md

-# How to write unit tests for gRPC C++ client.
-
-tl;dr: [Example code](https://github.com/grpc/grpc/blob/master/test/cpp/end2end/mock_test.cc).
-
-To unit-test client-side logic via the synchronous API, gRPC provides a mocked Stub based on googletest(googlemock) that can be programmed upon and easily incorporated in the test code. 
-
-For instance, consider an EchoService like this:
-
-
-```proto
-service EchoTestService {
-        rpc Echo(EchoRequest) returns (EchoResponse);
-        rpc BidiStream(stream EchoRequest) returns (stream EchoResponse);
-}
-```
-
-The code generated would look something like this:
-
-```c++
-class EchoTestService final {
-  public:
-  class StubInterface {
-    virtual ::grpc::Status Echo(::grpc::ClientContext* context, const ::grpc::testing::EchoRequest& request, ::grpc::testing::EchoResponse* response) = 0;
-  …
-    std::unique_ptr< ::grpc::ClientReaderWriterInterface< ::grpc::testing::EchoRequest, ::grpc::testing::EchoResponse>> BidiStream(::grpc::ClientContext* context) {
-      return std::unique_ptr< ::grpc::ClientReaderWriterInterface< ::grpc::testing::EchoRequest, ::grpc::testing::EchoResponse>>(BidiStreamRaw(context));
-    }
-  …
-    private:
-    virtual ::grpc::ClientReaderWriterInterface< ::grpc::testing::EchoRequest, ::grpc::testing::EchoResponse>* BidiStreamRaw(::grpc::ClientContext* context) = 0;
-  …
-  } // End StubInterface
-…
-} // End EchoTestService
-```
-
-
-If we mock the StubInterface and set expectations on the pure-virtual methods we can test client-side logic without having to make any rpcs.
-
-A mock for this StubInterface will look like this:
-
-
-```c++
-class MockEchoTestServiceStub : public EchoTestService::StubInterface {
- public:
-  MOCK_METHOD3(Echo, ::grpc::Status(::grpc::ClientContext* context, const ::grpc::testing::EchoRequest& request, ::grpc::testing::EchoResponse* response));
-  MOCK_METHOD1(BidiStreamRaw, ::grpc::ClientReaderWriterInterface< ::grpc::testing::EchoRequest, ::grpc::testing::EchoResponse>*(::grpc::ClientContext* context));
-};
-```
-
-
-**Generating mock code:**
-
-Such a mock can be auto-generated by:
-
-
-
-1.  Setting flag(generate_mock_code=true) on grpc plugin for protoc, or
-1.  Setting an attribute(generate_mock) in your bazel rule.
-
-Protoc plugin flag:
-
-```sh
-protoc -I . --grpc_out=generate_mock_code=true:. --plugin=protoc-gen-grpc=`which grpc_cpp_plugin` echo.proto
-```
-
-Bazel rule:
-
-```py
-grpc_proto_library(
-  name = "echo_proto",
-  srcs = ["echo.proto"],
-  generate_mock = True, 
-)
-```
-
-
-By adding such a flag now a header file `echo_mock.grpc.pb.h` containing the mocked stub will also be generated. 
-
-This header file can then be included in test files along with a gmock dependency.
-
-**Writing tests with mocked Stub.**
-
-Consider the following client a user might have:
-
-```c++
-class FakeClient {
- public:
-  explicit FakeClient(EchoTestService::StubInterface* stub) : stub_(stub) {}
-
-  void DoEcho() {
-    ClientContext context;
-    EchoRequest request;
-    EchoResponse response;
-    request.set_message("hello world");
-    Status s = stub_->Echo(&context, request, &response);
-    EXPECT_EQ(request.message(), response.message());
-    EXPECT_TRUE(s.ok());
-  }
-
-  void DoBidiStream() {
-    EchoRequest request;
-    EchoResponse response;
-    ClientContext context;
-    grpc::string msg("hello");
-
-    std::unique_ptr<ClientReaderWriterInterface<EchoRequest, EchoResponse>>
-        stream = stub_->BidiStream(&context);
-
-    request.set_message(msg + "0");
-    EXPECT_TRUE(stream->Write(request));
-    EXPECT_TRUE(stream->Read(&response));
-    EXPECT_EQ(response.message(), request.message());
-
-    request.set_message(msg + "1");
-    EXPECT_TRUE(stream->Write(request));
-    EXPECT_TRUE(stream->Read(&response));
-    EXPECT_EQ(response.message(), request.message());
-
-    request.set_message(msg + "2");
-    EXPECT_TRUE(stream->Write(request));
-    EXPECT_TRUE(stream->Read(&response));
-    EXPECT_EQ(response.message(), request.message());
-
-    stream->WritesDone();
-    EXPECT_FALSE(stream->Read(&response));
-
-    Status s = stream->Finish();
-    EXPECT_TRUE(s.ok());
-  }
-
-  void ResetStub(EchoTestService::StubInterface* stub) { stub_ = stub; }
-
- private:
-  EchoTestService::StubInterface* stub_;
-};
-```
-
-A test could initialize this FakeClient with a mocked stub having set expectations on it:
-
-Unary RPC:
-
-```c++
-MockEchoTestServiceStub stub;
-EchoResponse resp;
-resp.set_message("hello world");
-Expect_CALL(stub, Echo(_,_,_)).Times(Atleast(1)).WillOnce(DoAll(SetArgPointee<2>(resp), Return(Status::OK)));
-FakeClient client(stub);
-client.DoEcho();
-```
-
-Streaming RPC:
-
-```c++
-ACTION_P(copy, msg) {
-  arg0->set_message(msg->message());
-}
-
-
-auto rw = new MockClientReaderWriter<EchoRequest, EchoResponse>();
-EchoRequest msg;
-EXPECT_CALL(*rw, Write(_, _)).Times(3).WillRepeatedly(DoAll(SaveArg<0>(&msg), Return(true)));
-EXPECT_CALL(*rw, Read(_)).
-      WillOnce(DoAll(WithArg<0>(copy(&msg)), Return(true))).
-      WillOnce(DoAll(WithArg<0>(copy(&msg)), Return(true))).
-      WillOnce(DoAll(WithArg<0>(copy(&msg)), Return(true))).
-      WillOnce(Return(false));
-
-MockEchoTestServiceStub  stub;
-EXPECT_CALL(stub, BidiStreamRaw(_)).Times(AtLeast(1)).WillOnce(Return(rw));
-
-FakeClient client(stub);
-client.DoBidiStream();
-```
-